The objective of the present invention is to propose a method to prevent that the decryption of a keys file of a group of data stored in a storing unit (DB) of a decoder (STB), the latter comprising a security module (SM), allows many bad intentioned users to benefit illegally from this product.This method consists in extracting from an encrypted data flux the data to send towards the storing unit (DB) and to re-encrypt the data before transferring them to the storing unit (DB) by at least one specific key (K1, K2).